Mobile devices are in almost ubiquitous use in contemporary social, industrial and commercial endeavors. Mobile devices include familiar portable electronic computing and communicating devices such as cellular and “smart” telephones, personal digital assistants (PDA), laptop, “pad” style and handheld computers, calculators, and gaming devices. These and somewhat more specialized mobile devices, such as geo-locating/navigating and surveying equipment, electrical, electronic, test, calibration, scientific, medical, forensic/military and other instrumentation packages, have or provide a wide range and spectrum of utility.
In addition to networks, databases, and other communicative, computing and data storage and access infrastructures with which they operate, the utility of mobile devices is allowed, in no small part, by their components and related aspects and features of their function and interoperability. For example, a display component presents graphical information to users; often interactively, with a graphical user interface (GUI) and keyboard, haptic/voice activated and/or other inputs. A battery component comprises an electrochemical power source, which allows mobile devices to operate independently of outside power sources.
Of all mobile device components, the display typically consumes available battery power at the fastest rate and thus, contributes the most significant portion of power drain. During most use time and in most usage scenarios, display related computation remains fairly minor. Where display related computation may intensify, such as when a movie is viewed, increased computational load is typically handled quite efficiently with graphical processor unit (GPU) operations or the function of other dedicated components and circuits. Rather, the power demanded by its backlight subcomponent typically dominates the display's power drain.
An approach to reducing power drain and enhance mobile device effective battery life attempts to produce a visually equivalent image at lower display backlight intensities. For example, a lower power equivalent image version with a dimmed backlight may be rendered using a lightened (e.g., more transparent) liquid crystal display (LCD) subcomponent instance of the image. Equivalence of the low power image instance may thus be maintained, up to a point at which picture elements (e.g., pixels) in the image content may not be rendered without greater lightness or increased backlight emission.
Dynamic range compression (DRC; also referred to as contrast ratio compression) can maintain image instance equivalence beyond the point at which greater lightness or increased power is called for. For example, values stored in a look-up table (LUT) and/or a global or other tone mapping operator (TMO) may be used for DRC. DRC may also allow computation of local tone mapping (and/or color gamut related) changes to be computed over each image portion independently of (e.g., differently than) the other image portions, based on local contrast ratios.
DRC lowers overall dynamic range while preserving most of the image appearance. DRC is also useful for rendering high dynamic range (HDR) imagery and can improve image quality at lower backlight power levels, or can make the display usable with greater amounts of ambient light. However, computing DRC over each pixel of an image based on TMOs adds complexity and latency. In relation to TMO based DRC, LUT based approaches are simple to implement.
While the LUT-based approach may be simpler to implement, it is limited as to how much lightening may be reduced to conserve power before image modifications become visible. For example, excess reduction of backlight illumination for a mobile device flat panel display may cross a threshold related to a just noticeable difference (JND) or another visibility related metric. Thus, the image modification may likely cause an objectionable appearance to a significant number of viewers.
Approaches described in this section could, but have not necessarily been conceived or pursued previously. Unless otherwise indicated, neither approaches described in this section, nor issues identified in relation thereto are to be assumed as recognized in any prior art merely by inclusion therein.